Haloperidol may cause decreased blood levels of iron.¹ The importance of this interaction remains unclear. Iron should not be supplemented unless a deficiency is diagnosed.

Haloperidol may cause hyponatremia (low blood levels of sodium).² The incidence and severity of these changes remains unclear.

In a double-blind trial, supplementation of schizophrenic patients with Ginkgo biloba extract, in the amount of 250 mg per 2.2 pounds of body weight per day for 12 weeks, enhanced the effectiveness of haloperidol and also reduced the side effects of the drug.³

In a preliminary trial, daily supplementation with omega-3 fatty acids (360 mg of eicosapentaenoic acid plus 240 mg of docosahexaenoic acid), 800 IU of vitamin E, and 1,000 mg of vitamin C for four months decreased the severity of abnormal movements (akathisia) caused by haloperidol.⁴

Haloperidol and related antipsychotic drugs can cause a movement disorder called tardive dyskinesia. Several double-blind studies suggest that vitamin E may be beneficial for treatment of tardive dyskinesia.⁵ Taking the large amount of 1,600 IU per day of vitamin E simultaneously with antipsychotic drugs has also been shown to lessen symptoms of tardive dyskinesia.⁶ It is unknown if combining vitamin E with haloperidol could prevent tardive dyskinesia.

Haloperidol may cause liver damage. A double-blind study in 60 women treated with drugs such as haloperidol were given 800 mg per day silymarin extract made from milk thistle (Silybum marianum).⁷ Test subjects who were given silymarin experienced a significant decrease in free radical levels, unlike those given placebo.

Two double-blind studies have found that 0.4–0.8 mg/kg body weight per day of glycine can reduce the so-called negative symptoms of schizophrenia when combined with haloperidol and related drugs.^{8 , 9} Negative symptoms include reduced emotional expression or general activity. The action of glycine in combination with the drugs was greater than the drugs alone, suggesting a synergistic action. Another double-blind study using approximately half the amount in the positive studies could not find any benefit from adding glycine to antipsychotic drug therapy.¹⁰ Patients with low blood levels of glycine appeared to improve the most when given glycine in addition to their antipsychotic drugs.¹¹ No side effects were noticed in these studies, even when more than 30 grams of glycine were given daily.

Coffee and tea are reported to cause precipitation of haloperidol in the test tube.¹² If this interaction happens in people, it would reduce the amount of haloperidol absorbed and the effectiveness of therapy. People taking haloperidol may avoid this possible interaction by taking haloperidol one hour before or two hours after drinking coffee or tea.

Coffee and tea are reported to cause precipitation of haloperidol in the test tube.¹³ If this interaction happens in people, it would reduce the amount of haloperidol absorbed and the effectiveness of therapy. People taking haloperidol may avoid this possible interaction by taking haloperidol one hour before or two hours after drinking coffee or tea.

Haloperidol may cause hyperkalemia (high blood levels of potassium) or hypokalemia (low blood levels of potassium).¹⁴ The incidence and severity of these changes remains unclear. Serum potassium can be measured by any doctor.